1. Field of the Invention
The subject invention relates to a zero insertion force electrical connector for interconnecting electrical conductors to circuitry on a printed circuit board.
A need exists within the electronics industry for direct connection of conductors to the printed circuit board. This connector should also provide for easy insertion and withdrawal of the conductors.
Multiconductor cable and flexible printed circuits are interconnected to printed circuit boards for the distribution of dc power to the printed circuit boards and for data distribution to and from the circuitry on the printed circuit boards. Typically, the conductors are interconnected to an electrical female connector similar to those shown in U.S. Pat. Nos. 4,435,035 and 4,062,610; or in International Patent Application Number PCT/US86/01942 which is Publication Number WO87/01870; while a male post header is electrically interconnected to the printed circuit board. While this system is suitable for many such interconnections, the finished cost is increased by the inclusion of the male header. Therefore, there exists within the electronics industry a need for an electrical connector which will be suitable for mounting on the printed circuit board without the requirement for the male header; in other words, a connector where the electrical conductors can be directly interconnected to the connector.
A connector designed for the above mentioned application has a number of desired features. One desired feature is for improved mechanical advantage to lift the contacts from an opposed to an open position. The terminals should also be prestressed to allow maximum contact force on the electrical conductors. Another is to provide an electrical connector having a detent position where the contacts can be opened to a position where the contacts remain open for insertion of the flexible cable. This will require only one hand for insertion of the flexible cable.
The connector design should also be versatile, where the housing and basic terminal design can be used for a number of configurations. The connector should be available in a low height version for packaging purposes, or be in a vertical standing relation where access is a problem. The connector should also accommodate individual conductors of a multiconductor flat cable, printed circuit boards, or flexible printed circuitry. Finally, the design should be versatile enough to include electrical shielding.
One connector is shown in EP Publication 0 263 296 where the flexible circuit can be placed in the front face of the connector, and interconnected to a printed circuit board. In this connector, an upper cover is rotatable about the housing and a front nose of the cover lifts the contacts out of contact. This embodiment, while meeting some of the industry requirements, also has several disadvantages. First, the cover is placed on the top face of the connector which actually raises the vertical dimension further. Second, the cover is a lever, or fulcrum, which requires that the back portion of the cover must be pressed down in order to lift the contacts for insertion of the flexible cable. This requires that both hands are required for insertion of the cable, which, depending on available space within the electronics area, may not be available. Third, due to the small amount of vertical downward movement available, the connector does not provide much mechanical advantage for lifting the contacts, which again, may require for an awkward and difficult insertion of the wires or printed circuits. Lastly, this design does not allow for a variety of configurations. For example, this design could not be used, if desired, with the vertical arrangement, if needed. Also, this design does not lend itself well to adding features such as shielding, since so much of the upper portion of the connector must be accessible for the rotating cover.
U.S. Pat. Nos. 4,252,389 and 4,252,392 show electrical connectors which interconnect flat cable conductors to traces on printed circuit boards. These connectors also include cam members which move the cantilever springs out of contact with the cable, for installation of the cable without an insertion force. These cantilever springs do not however, contact the conductors of the flat flexible cable, but rather only spring load the conductors of the flat flexible cable into direct contact with the traces on the printed circuit board. In other words, the flat flexible cable has conductors open on one face, and that face is placed directly against the printed circuit board traces, while the spring members bias the cable towards the board. The springs never contact the conductors directly, but only the insulation which backs the conductor. While this system is usable for certain situations, this system has several limitations making it unusable for discrete solid conductors in a multi-conductor cable has heretofore required.